• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2012.10a
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• pp.75-80
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• 2012

Helmholtz resonator is widely used acoustic instrument which has high absorption characteristics at its resonance frequency. Particularly it maintains good performance even in the low frequency region that is difficult to control by general porous absorptive materials. However, under severely high sound pressure level, the absorption characteristics are changed by increase of resistance due to nonlinear behavior of neck impedance. Because of this nonlinear behavior, it is difficult to obtain the expected absorption performance under high sound pressure environment. Thus, in order to prevent excessive rise of resistance, the resonator with neck having cross section dimension decrease away from the entry of the resonator cavity could be suggested. This paper introduces the experiment method and results about nonlinear characteristics of Helmholtz resonator with tapered neck and proposes the approximate nonlinear impedance model.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.42 no.1
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• pp.9-17
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• 2005

We studied the characteristics of impedance and electromechanical coupling coefficient in ZnO and AIN thin films by using resonance frequency spectrum method. The response peak of impedance decreased with the decrease of thickness of piezoelectrics, the number of mode of response peak decreased with the decrease of substrate thickness. An error of Kt² estimated from input Kt² increased as the thickness of piezoelectrics decreased and the thickness of substrate increased. Also, the error was increased in case of a large acoustic impedance of substrate. It was found that the composite resonator operating in optimized condition could be designed through the resonance frequency spectrum analysis of composited resonator consisted of piezoelectric thin film and substrate.

• Journal of KSNVE
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• v.5 no.4
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• pp.577-583
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• 1995

The sandwich type piezoelectric resonator is widely used for the acoustic sources of underwater acoustic transducers, whose important design parameters are shapes, materials, dimensions and supporting methods. Practical design method of resonators consists of manufacturing, experiments and modification so that it requires much time and expenses. In this study, an analytical design method of sandwich type piezoelectric resonators is presented based on the nonlinear optimization technique. The proposed method is applied to the design of an example resonator model in order to maximize the output powers. For the investigation of performance according to the division and their electrical connection, three types of resonators are manufactured. In addition, their dynamic characteristics such as electrical admittance and transmitting voltage response are measured and compared.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.12
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• pp.1077-1079
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• 2003

This paper describes the development of bulk acoustic wave (BAW) resonators using a PolyVinyliDene Fluoride (PVDF). The resonators have an air gap between a substrate for acoustic isolation without surface micromachining. We measured the resonance frequency and the input reflection coefficient (S$\sub$11/) of resonators using vector network analyzer. The fundamental resonance in this experimental result was measured at 1.4 ㎓ with a return loss of -23.2 ㏈. We can confirm a possibility of resonator application as using a PVDF because it can fabricate the resonator without etching process.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.838-841
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• 2003

The aim of the study is to scrutinize the relationship between the area of resonance and insertion loss by analyzing the characteristics of 2-port resonator. This was done through designing an air-gap type Film Bulk Acoustic Resonator (FBAR) by using CAD model for the application of bandpass filter of high-frequency band with piezoelectric thin film. Moreover, through the design of ladder-type BPF, we were able to observe changes in bandwidth, resonation, out-of-band rejection depending on the number and area of resonator.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2000.11a
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• pp.95-98
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• 2000

Film bulk acoustic resonator used in microwave region can be analyzed by one-dimension Mason's model and one-dimensional numerical method, but it had several constraints to analyze effects of area variation, electrode-area variation, electrode-shape variation and spurious characteristics. To overcome these constraints film bulk acoustic resonator must be analysed by three dimensional numerical method. So, in this paper three dimensional finite element method was used to analyze several moles of resonance and was compared with the one dimension Mason's model analysis and analytic solution.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2005.11b
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• pp.114-117
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• 2005

In the reactive concentric resonator, perforated inner tubes are widely used for various purposes related to noise reduction, flow guiding, and structural aspects. Perforation distribution patterns influence both the acoustic performance and mechanical performance. In this study, the influence of distribution patterns on acoustic performance are explained by adopting the concept of extended inlet/outlet length. Predicted transmission with varying extended inlet/outlet length is compared with prediction by varying distribution patterns. The transmission loss difference due to perforation distribution patterns can be explained by changing the extended inlet/outlet length of the uniformly perforated resonator.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.11a
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• pp.275-278
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• 2003

The aim of the study is to scrutinize the relationship between the area of resonance and center frequency with varying thickness by analyzing the characteristics of 2-port resonator. This was done through ideal design using Leach model equivalent model modified Mason model equivalent circuit for the application of bandpass filter high-frequency band with resonator Moreover, through the design of ladder-type BPF, we were able to observe changes in bandwidth, resonation, out-of-band rejection depending on the number and area of resonator.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2010.11a
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• pp.610-613
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• 2010

A horizontal Rijke tube with an electric heating part is a convenient system for studying the thermo acoustic instability. In this work, horizontal Rijke tube is manufactured to investigate and compare damping characteristics of Helmholtz resonator under unsteady heat release and room temperature conditions. We obtained basic data using the Helmholtz resonator which is used as passive damper under the thermo acoustic instabilities.

• Journal of the Korean Society of Marine Environment & Safety
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• v.26 no.7
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• pp.915-921
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• 2020

Thermoacoustic instability caused by air conditioning in a combustion chamber has emerged as a problem that must be solved to establish a stable combustion system. Thermoacoustic instability is largely divided into primary and secondary acoustic instability. In this study, an experimental study of the effects of heat losses was conducted to investigate the mechanism of secondary acoustic instability. To generate the secondary acoustic instability, a quarter-wavelength resonator with one open end and one closed end was used, and the inside of the resonator was filled with premixed gases. Subsequently, secondary acoustic instability with downward-propagating flames could be realized via thermal expansion on the burnt side. To control heat losses qualitatively, an additional co-axial tube was installed in the resonator with air or nitrogen supply. Therefore, additional diffusion flames can be formed at the top of the resonator depending on the injection of the oxidizer into the co-axial tube when rich premixed flames are used. Consequently, secondary acoustic instability could not be achieved by increasing heat losses to the ambient when the additional diffusion flame was not formed, and the opposite result was obtained with the additional diffusion flame.